1. Field of the Invention
This invention relates to the control of brightness perceived by the human eye, and more particularly to a method and apparatus that achieves such control using a nodalized time-varying shutter (NTVS).
2. Description of the Prior Art
A premilinary patentability and novelty search conducted in connection with the invention or inventions disclosed herein has revealed the existence of the following United States Patents:
______________________________________ 3,245,315 3,409,909 3,441,513 3,575,491 3,576,761 3,585,381 3,591,810 3,603,305 3,630,603 3,617,374 3,620,889 3,661,142 3,692,388 3,704,625 3,720,623 3,893,340 4,087,575 4,180,722 4,261,651 4,272,164 4,278,349 4,393,400 ______________________________________
Of the patents listed above, five appear to be more pertinent than the others. These are identified as U.S. Pat. Nos. 3,245,315; 3,409,909; 3,603,305; 3,630,603 and 4,272,164.
Referring to these patents in the order in which they issued, it is noted that U.S. Pat. No. 3,245,315 discloses a light controlling device that is particularly adapted to protect the eyes from flashblindness. A sensor mounted on the spectacle frame "sees" the flash and initiates the application of an electric charge on the electro-optic crystal material included in the lenses, resulting in the lenses becoming opaque for the duration of the flash and then reverting to transparency. Also disclosed by this patent is a method for controlling brightness by reducing the steady-state light intensity reaching the eyes of the wearer of the spectacles through adsorption of the light impinging on the lenses. This mode of operation is fundamentally different from the mode disclosed and claimed herein wherein the brightness of a source of light is not diminished per se, but the perception of brightness is controlled by reducing the time that the light impinges on the eyes.
U.S. Pat. No. 3,409,909 discloses a device to protect against flashblindness of the type that might be imposed by the explosion of an atomic bomb. A light sensor initiates the release and dispersion of an opaque liquid on the interior of a cavity between two transparent lenses, thus attenuating the light seeking to pass through the lenses.
U.S. Pat. No. 3,603,305 does not relate to brightness control. Rather, this patent is directed to a sensory development apparatus, conveniently in the form of spectacles, useful to aid in the "fusion" process that occurs in the brain of a human to perceive the images transmitted to the retina of the eyes. Stated in other words, the apparatus described by this patent is particularly useful to aid visually impaired individuals to achieve visual fusion.
U.S. Pat. No. 3,630,603 describes spectacles incorporating lenses that can be darkened to reduce the steady-state light level reaching the eyes. Brightness control is achieved through steady-state dimming as with conventional sunglasses.
U.S. Pat. No. 4,272,164 describes a device to protect image intensifiers from glare using an electochemical material.
Thus, it will be seen that the devices discussed above all reduce the steady state light level by turning partially or totally opaque with the level of brightness controlled by the degree of opacity as in conventional sunglasses. This is clearly different from the invention disclosed herein which controls perceived brightness by controlling the fraction of time during which ambient light, ideally with minimum alteration, enters the eye.
Everything that a human sees is light-packets of energy called "quanta" that move in waves as a small part of the band of electromagnetic radiation that reaches Earth from the stars and galaxies, or from some artificial source of such light. The human eye is so sensitive to light that it has been stated that as few as ten quanta, roughly equivalent to the glow of a candle at a distance of ten miles, will stimulate the human eye. The Mammalian eye has evolved to function over a wide range of ambient light levels. Since the retina has a limited capacity to handle different levels of light intensity, nature has provided other structures to expand this range. Thus, the iris provides the primary mechanism for controlling the amount of light entering the eye. The eyebrows together with the squinting reflex both shade the eye from direct sunlight and help provide another means of coping with excessively bright light conditions. Mankind has heretofore assisted nature by inventing conventional sunglasses which reduce the amount of steady-state light reaching the retina by filtering the light with semi-transparent glass or plastic material. All these structures: the iris, squinting and conventional sunglasses allow the eye to function in brighter light by reducing the steady-state light intensity reaching the retina.
Accordingly, one of the important objects of the present invention is the provision of a method and apparatus for controlling the perceived brightness of light from a source thereof when viewed by a human eye.
Another object of the invention is the provision of a method and apparatus for controlling the perceived brightness of light from a source thereof by controlling the time of exposure of the eyes to the light.
Still another object of the invention is the provision of a method and apparatus for controlling the perceived brightness of light from a source thereof by periodically interrupting the light to which the eyes are simultaneously exposed at a frequency that is undetectable by the human eye.
Yet another object of the invention is the provision of a method and apparatus, including a pair of spectacles having lenses therein, operative to control the time interval during which light passes through the lenses to control the perception of brightness of the light impinging on the eye.
A still further object of the invention is the provision of a method and apparatus, including a pair of spectacles having lenses therein for the simultaneous admission of light to both eyes, wherein both lenses include a layer of liquid crystal material the transparency of which may be controlled by the application of an electric voltage.
Yet another object of the invention is the provision of a method and apparatus for controlling the perceived brightness of a source of light viewed by human eyes, including a pair of spectacles having lenses incorporating liquid crystal material the transparency of which may be selectively controlled by the application of an electric voltage, the area of the lenses being "nodalized" to define areas of the lenses that automatically react independently of other areas thereof to reduce the perceived brightness of light passing through a given "node."
One of the problems that has vexed the sunglass industry has been the inability to provide sunglasses for human wear that did not alter the perception of color by the wearer. Accordingly, another object of the present invention is the provision of a pair of spectacles including lenses equipped with means for controlling the brightness of the light impinging on the human eye while minimally distorting the color content of the light perceived.
A still further object of the invention is the provision of a method of interdependently controlling multiple nodes of a "nodalized" transparent body to control both brightness and contrast between "nodalized" areas of the transparent body.
The invention possesses other objects and features of advantage, some of which, with the foregoing, will be apparent from the following description and the drawings. It is to be understood however that the invention is not limited to the embodiment illustrated and described since it may be embodied in various forms within the scope of the appended claims.